Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Quais instituições se juntaram em 1993.
 ###Tabelas: CREATE TABLE list_of_songs_released_in_2007 (list_of_songs_released_in_2007_id AUTO_INCREMENT PRIMARY KEY, Song title VARCHAR, Artist VARCHAR, Year INT, Genre VARCHAR, Single / Pack name VARCHAR, Release date VARCHAR, Family Friendly VARCHAR, Additional Rock Band 3 Features VARCHAR) CREATE TABLE by_season (by_season_id AUTO_INCREMENT PRIMARY KEY, Season VARCHAR, Race INT, Podium INT, Pole INT, FLap INT) CREATE TABLE security_features (security_features_id AUTO_INCREMENT PRIMARY KEY, Distribution VARCHAR, Compile time buffer checks VARCHAR, Mandatory access control VARCHAR, Software executable space protection VARCHAR, grsecurity VARCHAR, RSBAC VARCHAR) CREATE TABLE current_members (current_members_id AUTO_INCREMENT PRIMARY KEY, Institution VARCHAR, Location VARCHAR, Founded INT, Type VARCHAR, Enrollment INT, Joined VARCHAR, Nickname VARCHAR) CREATE TABLE list_of_hyperons (list_of_hyperons_id AUTO_INCREMENT PRIMARY KEY, Particle VARCHAR, Symbol VARCHAR, Makeup VARCHAR, Rest mass MeV / c 2 VARCHAR, Isospin I VARCHAR, Spin ( Parity ) J P VARCHAR, Commonly decays to VARCHAR)  
SELECT Institution FROM current_members WHERE Joined = 1993